Piñeiro-Fernández, Juan CarlosRabuñal Rey, RamónRomay-Lema, EvaChantres-Legaspi, YelcoSantos-Martínez, Ana MaríaBesteiro-Balado, YoanaSuárez-Gil, RoiPértega-Díaz, Sonia2026-04-272026-04-272025-11-25Piñeiro-Fernández JC, Rabuñal-Rey R, Romay-Lema E, Chantres-Legaspi Y, Santos-Martínez AM, Besteiro-Balado Y, Suárez-Gil R, Pértega-Díaz S. Trends in hospital admissions and clinical complexity in centenarians: a nationwide population-based study in Spain (2004-2020). Eur Geriatr Med. 2026 Apr;17(2):797-809.1878-7657https://hdl.handle.net/2183/48105[Abstract] Purpose: The aim of this study is to describe nationwide trends in clinical complexity, principal diagnoses, and in-hospital outcomes among centenarian hospital admissions in Spain, from 2004 to 2020. Methods: This study is a retrospective, population-based study using the Spanish National Hospital Discharge Database. All unplanned admissions of patients aged ≥ 100 years were analyzed across three periods (2004-2010, 2011-2015, 2016-2020). Trends in comorbidity, diagnoses, complications, mortality, and length of stay (LOS) were assessed using joinpoint regression models. Results: A total of 43,730 hospital admissions were analyzed. The prevalence of severe comorbidity rose from 17.6 to 31.8% (p < 0.001), and multimorbidity from 61.4 to 76.6% (p < 0.001), with parallel rises in dementia and other frailty-related conditions. Infections became the leading cause of admission (p < 0.001), particularly respiratory (from 18.4 to 26.1%), and urinary infections (from 4.2 to 7.9%). All types of in-hospital complications rose steadily, with an upward trend in patients with ≥ 3 complications, especially in the last 5 years (Annual percent changes (APC) = 14.9%; 95% confidence interval (CI) 9.7%; 20.4%) and among women (APC = 15.9%; 95% CI 10.7%; 21.5%). In-hospital mortality rose modestly (APC = 1.0%; 95% CI 0.5%; 1.6%), while average LOS decreased from 8.7 ± 10.5 to 7.3 ± 7.3 days (p < 0.001). Discharges to nursing homes increased from 2.1 to 4.8% (p < 0.001). Conclusion: Centenarians admitted to Spanish hospitals over the last two decades showed increasing clinical complexity and complications, with infections as the leading cause of admission and a modest rise in mortality despite a shorter LOS. These findings highlight the need to adapt healthcare models for this growing and vulnerable population.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/CentenariansComorbidityElectronic Health RecordsEpidemiologic studiesHospitalizationjournal articleopen access10.1007/S41999-025-01362-1